Industrial useful Field
This invention relates to a damper disc with serial torsion springs usable as a clutch disc assembled in an automobile, an agricultural machine or a construction machine etc., or as a marine damper.
Prior Art
A mechanism has conventionally been known, in which a pair of projecting hub-side flanges protruding radially outwardly are provided on a central hub, a pair of side plates fitting rotatably onto the hub and having holes extending in a disc circumferential direction are disposed on both sides of the hub-side flange, two retainers having respectively a pair of retainer-side flanges fitting rotatably onto the hub and protruding in a disc radial direction are disposed in between the hub-side flange and the side plates, each retainer-side flange and each hub-side flange are disposed and spaced approximately equally in the disc circumferential direction, and a coil spring extending approximately in the disc circumferential direction is interposed between the retainer-side flange & holes of side plates and the hub-side flange to resiliently couple the hub and the side plates in the disc circumferential direction (Japan Patent unexamined Publication (KOUKAI) No. 54-96651).
In this mechanism, however, a wide range of twist angle characteristic is obtainable as compared with a general torsion spring type damper disc, but on the other hand a twist rigidity characteristic can not be changed in multi-stages. Therefore, in the above mechanism, a small torsional vibration within a range of low twist angle can not be effectively absorbed when a twist rigidity is set high, and a torsional vibration can not be effectively absorbed in case where the torsional vibration is large when the twist rigidity is set low.
Problem to be solved by this invention
The above-mentioned conventional mechanism includes a problem that a wide range of twist angle characteristic can be obtained, but on the other hand sufficient vibration absorption effect can not be obtained because the twist rigidity characteristic can not be changed in multi-stages.
The present invention is intended to solve the above-mentioned problem by enabling the twist rigidity to be changed in two stages while taking the advantage of the wide twist angle characteristic which is a feature of the damper disc with serial torsion springs.
Countermeasures to solve the problem
A damper disc with serial torsion springs, in which a pair of projecting hub-side flanges protruding radially outwardly are provided on a central hub, a pair of side plates fitting rotatably onto the hub and having holes extending in a disc circumferential direction are disposed on both sides of the hub-side flange, a pair of retainers having respectively a pair of retainer-side flanges fitting rotatably onto the hub and protruding in a disc radial direction are disposed in between the hub-side flange and the side plates, a coil spring extending approximately in the disc circumferential direction is interposed between the retainer-side flange & holes of side plates and the hub-side flange to resiliently couple the hub and the side plates in the disc circumferential direction; characterized by that said coil spring is composed of a high-rigidity large-diameter main spring and a low-rigidity small-diameter sub spring fitted therein, one side of said pair of retainer-side flanges has a projection protruding to one side of the sub spring contacting therewith, another side of said retainer-side flanges has a projection protruding to another side of the sub spring, thereby the projection of said retainer-side flange is adapted to compress only the sub spring at an initial sage of twisting of the disc .